Synthesis of new TCH/Ni‐based nanocomposite supported on SBA‐15 and its catalytic application for preparation of benzimidazole and perimidine derivatives

A stable nickel‐decorated SBA‐15 nanocomposite (Ni/TCH@SBA‐15) was synthesized through surface modification of silica nanoparticles with 3‐chloropropyltriethoxysilane (CPTES) and thiocarbohydrazide (TCH) followed by metal–ligand coordination with Ni (II). The structure of this organometallic nanocomposite was characterized by Fourier transform‐infrared, field emission‐scanning electron microscopy, EDAX, transmission electron microscopy, atomic absorption spectroscopy and N₂ adsorption–desorption (Brunauer–Emmett–Teller) techniques. The catalytic performance of Ni/TCH@SBA‐15 (NNTS‐15) was determined for the synthesis of 2‐aryl‐substituted benzimidazoles and 2,3‐dihydroperimidines. The excellent yields within shorter reaction times, simplicity of catalytic methods, non‐toxicity and clean reactions, mild reaction conditions and easy work‐up procedure are the important merits of these synthetic protocols. Moreover, the Ni (II) bonded to the SBA‐15 surface was stable under the catalytic reaction conditions resulting in its efficient recycling and reuse.     

Light-induced dehydrogenation of 5-acetyl-2-methoxydihydropyrimidines

Tautomeric mixtures of 4-aryl substituted 5-acetyl-2-methoxydihydropyrimidines undergo oxidation by exposing to the UV-light under formation of sole pyrimidines. The nature of the 4-substitution and solvent, and the ratio of tautomeric mixtures affect the rate of reaction. A proposed electron transfer-induced photo-dehydrogenation supports the obtained results in this study.     

Optimization of temperature-controlled ionic liquid dispersive liquid phase microextraction combined with high performance liquid chromatography for analysis of chlorobenzenes in water samples

Temperature-controlled ionic liquid dispersive liquid phase microextraction (TCIL-DLPME) combined with high performance liquid chromatography-diode array detection (HPLC-DAD) was applied for preconcentration and determination of chlorobenzenes in well water samples. The proposed method used 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim][PF₆]) as the extraction solvent. The effect of different variables on extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the TCIL-DLPME were extraction solvent volume, salt effect, solution temperature, extraction time, centrifugation time, and heating time. The Plackett-Burman design was employed for screening to determine the variables significantly affecting the extraction efficiency. Then, the significant factors were optimized by using a central composite design (CCD) and the response surface equations were developed. The optimal experimental conditions obtained from this statistical evaluation included: extraction solvent volume, 75 μL; extraction time, 20 min; centrifugation time, 25 min; heating time, 4 min; solution temperature, 50 °C; and no addition of salt. Under optimal conditions, the preconcentration factors were between 187 and 298. The limit of detections (LODs) ranged from 0.05 μg L⁻¹ (for 1,2-dichlorobenzene) to 0.1 μg L⁻¹ (for 1,2,3-trichlorobenzene). Linear dynamic ranges (LDRs) of 0.5-300 and 0.5-500 μg L⁻¹ were obtained for dichloro- and trichlorobenzenes, respectively. The performance of the method was evaluated for extraction and determination of chlorobenzenes in well water samples in micrograms per liter and satisfactory results were obtained (RSDs < 9.2%).     

Hollow fiber-based liquid phase microextraction combined with high-performance liquid chromatography for the analysis of gabapentin in biological samples

Three-phase hollow fiber microextraction technique combined with high performance liquid chromatography-ultra violet (HPLC-UV) was applied for the extraction and determination of gabapentin in biological fluids. Gabapentin (GBP) was derivatized with 1-fluoro-2,4-dinitrobenzene, as a UV absorbent agent in borate buffer (pH 8.2) before extraction. The derivative product of GBP was extracted from the 8.5 mL of acidic solution (source phase) into an organic phase (dihexyl ether) impregnated in the pores of a hollow fiber and finally back-extracted into 24 μL of the basic solution (pH 9.1) located inside the lumen of the hollow fiber (receiving phase). The extraction took place due to pH gradient between the inside and outside of the hollow fiber membrane. In order to achieve maximum extraction efficiency, different parameters affecting the extraction conditions were optimized. Under the optimized conditions, preconcentration factor of 95 and detection limit (LOD) of 0.2 μg L⁻¹ were obtained. The calibration graph was linear within the range of 0.6-5000 μg L⁻¹. Finally, the feasibility of the proposed method was successfully confirmed by extraction and determination of GBP in human urine and plasma samples in the range of microgram per liter and suitable results were obtained (RSDs < 6.3%).     

Cinnamoylphenethyl amides from Polygonum hyrcanicum possess anti-trypanosomal activity

A methanolic extract from aerial parts of Polygonum hyrcanicum (Polygonaceae) showed high activity against Trypanosoma brucei rhodesiense (IC50 = 3.7 microg/mL). Bioassay-guided fractionation of the extract resulted in isolation of cinnamoylphenethyl amides, including N-trans-caffeoyltyramine (1), N-trans-p-coumaroyltyramine (7), and N-trans-feruloyltyramine (8) as the main active constituents (IC50s ranging from 2.2 to 13.3 microM). Some structurally related, but less active compounds, such as cannabisin B (2), tyrosol (3), p-coumaric acid (4), ferulic acid (5), and N-cis-feruloyltyramine (6) were also identified, along with N-trans-3,4-dimethoxycinnamoyldopamine (9). Cytotoxicity of the active compounds in L6 cells was determined, and selectivity indices (SI) of 7.9 to 33.4 were calculated.     

Highly Convergent One‐Pot Four‐Component Regioselective Synthesis of Spiro‐pyranopyrazoles and Oxa‐aza‐[3.3.3]propellanes

A concise and efficient route for the synthesis of spiro‐pyranopyrazoles and oxa‐aza‐[3.3.3]propellanes by simple regioselective multicomponent reaction of ninhydrin, malononitrile, hydrazine derivatives, and β‐keto esters or dimethyl acetylenedicarboxylate was developed. This protocol provides an alternative method for combinatorial and parallel syntheses in drug discovery. The value of this method lies in its simplicity, regioselectivity, and good yields. The structures of 3 and 4 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Schemes 2 and 3).     

An unexpected oxidative decarboxylation reaction of 2,3-dihydroxybenzoic acid in the synthesis of new dibenzyltetrahydroquinoxalinediones

Chemical and electrochemical oxidation of different catechols were carried out in the presence of N,N′-dibenzylethylenediamine (DBEDA) in a phosphate buffer/acetonitrile solution for the synthesis of different new dibenzyltetrahydroquinoxalinedione derivatives. The oxidation of catechol (1a), 2,3-dihydroxybenzoic acid (1e), and 3,4-dihydroxybenzoic acid (1d) led to the same product, probably due to the decarboxylation reaction of intermediates. An oxidative decarboxylation reaction of 3,4-dihydroxybenzoic acid (1d) has been reported before, while an unexpected oxidative decarboxylation reaction of 2,3-dihydroxybenzoic acid (1e) in the presence of DBEDA is reported for the first time.     

An Isocyanide‐Based Multicomponent Reaction: New Route for Synthesis of Isoxazolinedione Derivatives

An efficient and novel multicomponent reaction for synthesis of new isoxazolinedione has been described. This protocol involves reaction of two molecules of isocyanide, aliphatic oxime, alkylidene substituted Meldrum's acid, and water (moisture). Elemental analyses, IR, ¹H NMR, and ¹³C NMR spectroscopic data of products are consistent with the structure defined by X‐ray diffraction analysis.